Safety and Efficacy of Peptide Receptor Radionuclide Therapy in Multiple Endocrine Neoplasia Syndrome: A Single-center Experience

Purpose: Peptide receptor radionuclide therapy (PRRT) is recommended and approved in advanced neuroendocrine tumors (NETs). There is a lack of data on the utility of PRRT in multiple endocrine neoplasia (MEN) syndrome. This study explores the utility of PRRT in MEN syndrome patients with inoperable/metastatic NETs. Methods: A single-center retrospective analysis of MEN syndrome patients with advanced NETs referred for PRRT was done. Upto 4 cycles of 177 Lu-DOTATATE (5.5–7.4 GBq/cycle) were administered every 8–12 weeks. Treatment-related adverse events were assessed using CTCAE v5. The best response to PRRT was evaluated using RECIST 1.1. Follow-up was done to calculate the progression-free survival (PFS) and overall survival (OS). Results: The data of 15 patients with a median age of 36 years (IQR: 32–49) was analyzed. Fourteen patients had MEN-1 syndrome, and 1 had MEN-2 syndrome. Thirteen patients with MEN-1 syndrome had gastroenteropancreatic (GEP) NET, with the multifocal primary as the most common finding (n=7). One patient had thymic carcinoid. All patients had hyperparathyroidism, while 6 had pituitary adenoma. Fifty-three cycles of 177 Lu-DOTATATE (range: 1–4) were administered with a median cumulative activity of 27.8 GBq. Twelve patients (80%) showed grade 1/2 adverse events, with leukopenia being the most common. Six patients achieved partial response (43% ORR), 6 showed stable disease (86% DCR), 2 (14%) showed disease progression during PRRT, while 1 patient was lost to follow-up. The median PFS was 32.6 months (95% CI: 14.7–not reached) with an estimated 1- and 5-year PFS rate of 86.2% (95% CI: 68–100) and 46.3% (95% CI: 13–80), and estimated 5-year OS rate of 76.2% (95% CI: 52.1–100). Conclusion: 177 Lu-DOTATATE is a safe and effective treatment option for advanced NETs in MEN syndrome. However, large-sized multicentric prospective studies are required.